Heat pump system and method for operating said system

ABSTRACT

Methods and systems are provided for operating a climate control system. In one example, a method for operating a vehicle climate control system includes modeling a temperature in a cabin heating circuit coupled to a heat pump. The method also includes operating the heat pump to deliver thermal energy to a cabin heat exchanger based on the modeled temperature.

FIELD

The present description relates generally to methods and systems forvehicle cabin climate control.

BACKGROUND/SUMMARY

Vehicles have incorporated cabin climate control systems with, forexample, heater cores and air conditioning devices, to achieve desiredcabin conditioning set-points. Heat pump systems have also beenincorporated into vehicles to more efficiently heat and cool the cabin.Heat pump systems may be particularly beneficial in plug-in vehiclessuch as battery electric vehicles (BEVs) where energy conservation isdesirable. Heat pumps can, for example, increase a vehicle's range whencompared to systems using solely electrically operated heaters for cabinheating and separate air conditioning (A/C) loops for cabin cooling.However, vehicles may experience inefficient climate control energymanagement stemming from the heat pump control strategies employed inthe vehicle.

One example approach of incorporating a heat pump into a cabinconditioning system is shown by Ragazzi in U.S. 2015/0183296 A1. Ragazzidiscloses a vehicle cabin conditioning system controlling cabin heatingby operating a positive temperature coefficient (PTC) heater and a heatpump. A feedback PTC heater control strategy is employed in Ragazzi forcabin heating regulation.

Applicants have recognized several drawbacks with Ragazzi's cabinclimate control system and other cabin climate control strategies. Forexample, Ragazzi coordinates the use of the PTC heater with engineoperation. This PTC heater operating strategy is not applicable to BEVs,limiting the applicability of the system. Furthermore, in other vehicleheat pump systems a number of sensors inputs are in feedback controlstrategies for heat pump operation. The heat pump sensors may be costlyand therefore increase the vehicle system's manufacturing cost andcomplexity.

To address at least some of the abovementioned problems, a method foroperating a vehicle climate control system is provided. The methodincludes modeling a temperature in a cabin heating circuit coupled to aheat pump circuit via a refrigerant to coolant heat exchanger configuredto transfer thermal energy between the heat pump circuit and the cabinheating circuit. The method further includes operating the heat pumpcircuit to deliver thermal energy to a cabin heat exchanger based on themodeled temperature. In this way, a virtual temperature is modeled tofacilitate accurate cabin heating and rapid cabin warm-up. Virtualizingthe temperature also enables the number of temperature sensors used forcomponent control (e.g., feedback control) in the system to be reduced,if desired. Consequently, the system's manufacturing costs may bedecreased, resulting in decreased vehicle costs.

In one example, the method may further comprise, prior to operating theheat pump circuit, operating a heater positioned downstream of therefrigerant to coolant heat exchanger to deliver thermal energy to thecabin heat exchanger based on temperature data from a temperature sensorcoupled to a conduit extending between the electrically operated heaterand the cabin heat exchanger. In such an example the method may furthercomprise, decreasing an output of the electrically operated heaterresponsive to the vehicle cabin achieving a target temperature while theheat pump circuit continues to deliver thermal energy to the cabin heatexchanger to maintain the target temperature. In this way, both the heatpump and the electrically operated heater may be operated, in an initialstage, to rapidly warm the vehicle cabin, if desired, and during asubsequent stage, electrically operated heater operation may be phasedout while the heat pump maintains the cabin at a desired temperature orwithin a desired temperature range, resulting in increased energyconservation. Increasing system efficiency in the vehicle may beparticularly beneficial in BEVs where decreased energy consumption canincrease vehicle range.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic depiction of a vehicle.

FIG. 2 shows a climate control system for a vehicle operating in aheating mode.

FIG. 3 shows the climate control system, depicted in FIG. 2, operatingin a cooling mode.

FIG. 4 shows a method for operation of a climate control system.

FIGS. 5 and 6 illustrate use-case timing diagrams for climate controlsystem operating methods.

DETAILED DESCRIPTION

A vehicle climate control system designed to efficiently operate in bothheating and cooling modes using modeled temperatures and/or pressures isdescribed herein. The vehicle may be a passenger vehicle as is shown inFIG. 1 or a commercial vehicle (not shown). FIGS. 2 and 3 show anexample of a climate control system operating in different modes usingmodeled temperatures and pressures. FIG. 4 shows a method for efficientcontrol of a climate control system in a cooling mode using a modeledpressure and a heating mode using a modeled temperature. FIGS. 5 and 6show use-case graphical representations of the methods for modal vehiclesystem control.

Referring to FIG. 1, a vehicle 10 including an internal combustionengine 12, an electric motor 14, and an energy storage device 16 isshown. The engine 12 may include cylinders, valves, etc., to enable theengine to implement a combustion process (e.g., four stroke combustionprocess) for motive power generation. The electric motor 14 is designedto generate motive power using energy from the energy storage device 16and may include rotors, stators, etc., for power generation. A drivewheel 24 in the vehicle 10 may receive rotational energy generated viathe engine 12 and/or electric motor 14 to propel the vehicle along adrive surface (not shown). The drive wheel is illustrated as a frontwheel, however powertrain configurations such as two-wheel drive, rearwheel drive, four wheel drive, etc., have been envisioned.

In one example, the vehicle 10 may harness motive energy from both theengine 12 and the electric motor 14 and therefore may be referred to asa hybrid electric vehicle. Hybrid propulsion embodiments may includefull hybrid systems, in which the vehicle can run on just the engine,just the energy conversion device (e.g. motor), or a combination ofboth. Assist or mild hybrid configurations may also be employed, inwhich the engine is the primary torque source, with the hybridpropulsion system acting to selectively deliver added torque, forexample during tip-in or other conditions.

In other examples, the vehicle may include only electric motor 14 forpropulsion and therefore may be referred to as a battery electricvehicle (BEV). The electric motor 14 may be supplied with electricalpower via the energy storage device 11 (e.g., battery, capacitor,flywheel, etc.) Energy storage device may be recharged from an externalenergy source such as a stationary electrical power grid 17 (e.g., homeor remote charging station), a portable energy source, solar chargingstation, etc., via electrical plug 18, capacitive charging, etc.

The engine 12 and/or electric motor 14 may be controlled at leastpartially by a control system 19 including controller 20. Controller 20may receive various signals from sensors 21 coupled to the engine 10and/or electric motor 14 and send control signals to various actuators22 coupled to the engine, motor, and/or vehicle to enable output of theengine and/or motor to be adjusted as desired.

FIGS. 2 and 3 show a climate control system 200. It will be understoodthat the climate control system 200 illustrated in FIG. 2 may beincluded in the vehicle 10 shown in FIG. 1, or other suitable vehicles.As such, the vehicle 10, shown in FIG. 1, may include common components,functionality, etc., with the system shown in FIGS. 2 and 3 or viceversa. As such, the energy storage device 248, shown in FIGS. 2 and 3 isan example of the energy storage device 11, shown in FIG. 1, thecontroller 250 may be an example of the controller 20, shown in FIG. 1,etc.

The climate control system 200 includes a cabin heating circuit 202,heat pump circuit 204, and an energy storage device cooling circuit 206.However, other system configurations have been contemplated withadditional or alternate cooling and/or heating loops, additional oralternate coolant and/or refrigerant routing, etc. The working fluid inthe heat pump circuit 204 may be refrigerant. On the other hand, theworking fluid in the cabin heating circuit 202 and the energy storagedevice cooling circuit 206 may be a suitable coolant such as a mixtureof water and glycol, a waterless coolant, etc. As described herein, acircuit is a grouping of conduit(s), line(s), pump(s), valve(s), heatexchanger(s), etc., routing a working fluid (e.g., refrigerant, coolant,etc.,) along a desired path.

The cabin heating circuit 202 includes a cabin heat exchanger 208 (e.g.,heater core). The cabin heat exchanger 208 is designed to transfer heat,indicated via arrow 210, to a vehicle cabin 212. For instance, the cabinheat exchanger 208 may heat air in a ventilation system directing theheated air into the vehicle cabin. The cabin heat exchanger 208 and/orthe other heat exchangers described herein may include conduits, fins,housings, etc., to accomplish the heat transfer functionality.

The cabin heating circuit 202 may further include an electricallyoperated heater 214 (e.g., resistance heater, a positive temperaturecoefficient (PTC) heater, thermoelectric heater (e.g., Peltier heater,etc.) The electrically operated heater 214 may heat coolant flowingthrough the conduit 216 during certain operating conditions. The heater214 is shown positioned downstream of the first refrigerant to coolantheat exchanger 226. By arranging the heater 214 downstream of the heatexchanger 226 the vehicle cabin may be quickly warmed up using bothdevices and then the heat pump may subsequently take over cabin heatingoperation when it has achieved a desired operating state. In this way,the cabin can be first rapidly heated and then the system may be moreefficiently operated subsequent to the rapid cabin warm-up. However,other arrangements of the heater 214 and the heat exchanger 226 havebeen contemplated.

The cabin heating circuit 202 may further include a valve 218 that mayprovide fluidic coupling between the cabin heating circuit 202 and theenergy storage device cooling circuit 206, during some conditions, andinhibit coolant flow between the cabin heating circuit 202 and theenergy storage device cooling circuit 206, during other conditions.Thus, the valve 218 during some conditions may provide fluidic couplingbetween an outlet of the electrically operated heater 214 and an inletof the cabin heat exchanger 208 via coolant line 219. However, duringother conditions the valve 218 may provide fluidic coupling between theoutlet of the electrically operated heater 214 and coolant conduit 221in the energy storage device cooling circuit 206. It will be understoodthat the valve 218 and the other valves described herein may be arrangedin a various configuration to permit and block working fluid flow therethrough. Additionally, the valves may also be arranged in flowconfigurations between opened and closed (e.g., partially opened orpartially closed) where a desired amount of working fluid (e.g.,coolant, refrigerant, etc.,) is provided to downstream devices,components, etc.

The cabin heating circuit 202 may also include a pump 220 designed toadjust coolant flow through the circuit. For instance, the pump 220 mayincrease or decrease coolant flow through the cabin heating circuit 202based on engine operating conditions. The pump 220 as well as the otherpumps described herein may include pistons, housings, chambers, rotors,etc., to accomplish said coolant flowrate adjustment. Moreover, the pump220 as well as the other pumps described herein may be electricallydriven. However, mechanically driven pumps have been envisioned when thesystem is included in a hybrid vehicle with an engine. A coolant conduit222 provides fluidic coupling between an inlet of the pump 220 and thecabin heat exchanger 208. Another coolant conduit 224 provides fluidiccoupling between an outlet of the pump 220 and a first refrigerant tocoolant heat exchanger 226.

The first refrigerant to coolant heat exchanger 226 provides heattransfer between the cabin heating circuit 202 and the heat pump circuit204, when in operation. It will be understood that the first refrigerantto coolant heat exchanger 226 as well as the other refrigerant tocoolant heat exchangers described herein may fluidly isolate coolant andrefrigerant flowing there through but enable heat transfer between thecoolant and the refrigerant.

The heat pump circuit 204 may include the first refrigerant to coolantheat exchanger 226 along with a compressor 228, an accumulator 230, anevaporator 232, a first expansion valve 234 (e.g., cooling expansionvalve), an exterior heat exchanger 236, and a second expansion valve 238(e.g., heating expansion valve). The compressor 228 is designed toincrease the pressure of the refrigerant flowing there through and mayinclude a housing, rotor, vanes, other suitable components, etc., toachieve the refrigerant pressurization. The accumulator 230, when inoperation, may act as a reservoir for storing residual liquidrefrigerant so that vapor refrigerant rather than liquid refrigerant maybe provided to the compressor 228. The accumulator 230 may include adesiccant that absorbs small amounts of water moisture from therefrigerant, in some embodiments.

The second expansion valve 238 may control the amount of refrigerant(e.g., superheat) delivered to the exterior heat exchanger 236.Additionally, the first expansion valve 234 may control the amount ofrefrigerant (e.g., subcool) delivered to the evaporator 232. The firstexpansion valve 234 and the other expansion valves herein may includesprings, temperature sensors, orifices, etc., to accomplish therefrigerant metering.

The heat pump circuit 204 may further include a second coolant torefrigerant heat exchanger 240. The second coolant to refrigerant heatexchanger 240 may when in operation, transfer thermal energy between therefrigerant in the heat pump circuit 204 and the energy storage devicecooling circuit 206. An expansion valve 242 meters the amount ofrefrigerant delivered to the second coolant to refrigerant heatexchanger 240.

The energy storage device cooling circuit 206 includes a pump 244, anenergy storage device cooler 246 coupled to or otherwise integrated intoan energy storage device 248, a coolant conduit 249 routing coolantthrough the second refrigerant to coolant heat exchanger 240, in theillustrated example. However, other suitable energy storage devicecooling circuit arrangements have been envisioned. The energy storagedevice cooler 246 may include conduits, passages, etc., allowing coolantto be routed through the energy storage device, across the housing ofthe energy storage device, etc. The coolant conduit 221 also extendsbetween the energy storage device cooler 246 and the valve 218. Anothercoolant conduit 247 also extends between the second refrigerant tocoolant heat exchanger 240 to an inlet of the pump 244.

FIGS. 2 and 3 also show a controller 250 in the vehicle climate controlsystem 200. Specifically, controller 250 is shown in FIGS. 2 and 3 as aconventional microcomputer including: microprocessor unit 251,input/output ports 252, read-only memory 253, random access memory 254,keep alive memory 255, and a conventional data bus. However, numerouscontroller arrangements have been envisioned.

The controller 250 may be configured to trigger one or more actuatorsand/or send commands to components. For instance, the controller 250 maytrigger adjustment of the valve 218, pump 220, compressor 228, expansionvalve 234, expansion valve 238, expansion valve 242, pump 244, valve289, and/or electrically operated heater 214. Specifically in oneexample, the controller 250 may send signals to an actuator in the pump220 to induce adjustment (e.g., increase or decrease) in coolant flow.The other adjustable components receiving commands from the controllermay also function in a similar manner. Therefore, the controller 250receives signals from the various sensors and employs various actuatorsto adjust system operation based on the received signals andinstructions stored in memory (e.g., non-transitory memory) of thecontroller. As another example, the controller 250 may make a logicaldetermination regarding a positon of an actuator in a commandedcomponent based on logic rules that are a function of a parameter (e.g.,coolant temperature, refrigerant pressure, etc.) The controller may thengenerate a control signal that is sent to the actuator. The controlsignal, for instance, may be generated using a look-up table indexed tooperating conditions. However, other suitable schemes for determiningthe make-up of control signals sent to actuators in controllablecomponents have been envisioned.

The controller 250 may also receive signals from sensors in the climatecontrol system 200 and/or engine 12, shown in FIG. 1. The sensorsproviding input into the controller may include a pressure sensor 270, atemperature sensor 272, a temperature sensor 274, temperature sensor275, ambient temperature sensor 290, and/or ambient pressure sensor 292.Additionally, the controller 250 is also configured to receive a pedalposition from a pedal position sensor 256 couples to a pedal 257actuated by an operator 258.

A possible location of a modeled pressure, discussed in greater detailherein is indicated at 276. Additionally, a potential location of amodeled temperature discussed in greater detail herein is indicated at278. However, it will be understood that the pressures and/ortemperatures may be modeled at additional or alternate suitablelocations in the system. It will be appreciated that when thetemperature and pressure are modeled sensors may be omitted from thesystem at those locations, thereby reducing system costs. It will alsobe appreciated that the controller 250 may determine the occurrence ofdifferent events, conditions, etc., from the sensor inputs.Additionally, the controller 250 may receive cabin heating/coolingrequests from an input device 280. The input device may be a controlpanel in the vehicle cabin, a portable computing device, etc. Forexample, a user may interact with the control panel (e.g., a temperatureknob, slider, touch interface, combinations thereof, etc.,) to set thecabin at a desired temperature and set the system to output a targetedamount of cabin cooling or heating. In this way, a vehicle driver,passenger, etc., can request cabin heating or cooling. In otherexamples, the cabin temperature set-point may be adjusted according to apredetermined schedule. Additionally, controller 250 may be programmedwith computer readable data representing instructions executable toperform the methods, controls schemes, etc., described below as well asother variants that are anticipated but not specifically listed.

It will be understood that the controller 250 is designed to operate theclimate control system 200 in different modes. FIG. 2 specifically showsa first operating mode (e.g., heating mode) of the climate controlsystem 200. In the first operating mode, coolant is heated via the heatpump circuit 204 and then heated coolant is transferred to the cabinheat exchanger 208. Specifically, in the illustrated example, the heatpump circuit 204 is operated to flow refrigerant from the compressor 228to the first refrigerant to coolant heat exchanger 226, indicated viaarrow 282. The first refrigerant to coolant heat exchanger 226 transfersthermal energy from the refrigerant to coolant in the cabin heatingcircuit 202. Refrigerant is flowed through the expansion valve 238 andthen to the exterior heat exchanger 236, indicated at arrow 284, wherethermal energy is transferred from the refrigerant to the surroundingenvironment. Refrigerant is then routed from the exterior heat exchangerto the accumulator 230 for the compressor 228, bypassing the evaporator232, indicated via arrows 286. However, other refrigerant routingschemes for the heating mode has been contemplated.

A valve 289 (e.g., shut-off valve) is shown positioned in the conduit291. Additionally or alternatively, a valve (not shown) may bepositioned in the conduit 293. Thus, the valve 289 is positioned betweenthe junction 295 and junction 297. The climate control system 200 isshown including other junctions that are not specifically labelled. Thejunctions in the system 200 function to allow fluid flow from differentconduits to merge and may include housings, sections, etc., toaccomplish the flow merging functionality. Additionally, the system isalso shown including conduits extending between the junctions and othercomponents that are not specifically labelled. The conduits function toallow fluid to flow between the components and may include housings,interior flow channels, etc., to accomplish the fluid transportfunctionality. The valve 289 may be operated to restrict the flow ofrefrigerant through the conduit 291, during certain operatingconditions. Restricting the flow through the conduit 291 via the valve289 reduces the chance (e.g., prevents) refrigerant from bypassing valve234 and/or expansion valve 242 through conduit 291 and back to thecompressor when flow is desired through the valve 234 and/or expansionvalve 242.

In the cabin heating circuit 202, in the heating mode, the pump 220 isoperated to flow coolant through the first refrigerant to coolant heatexchanger 226, through the electrically operated heater 214, through thevalve 218, to the cabin heat exchanger 208, and then returning to aninlet of the pump 220, indicated via arrows 288. In this way, thecoolant travels in a loop to deliver heated coolant to the cabin heatexchanger 208 (e.g., heater core) to facilitate cabin heating. It willbe understood that the electrically operated heater 214 during someconditions, may be activated during the heating mode to assist in cabinheating. In this way, the electrically operated heater and heat pump canboth provide cabin heating, facilitating rapid cabin warming. However,in other examples, the electrically operated heater may not be operatedduring the heating mode. It will therefore be understood, that theheating mode may be conceptually divided into sub-modes, a firstsub-mode where the electrically operated heater and the heat pumpcircuit are operated in conjunction to provide heat to the vehicle cabinand a second sub-mode where electric heating of the cabin is reduced(e.g., phased out) and the heat pump circuit efficiently providesvehicle cabin heating. For example, in the second sub-mode, electricheater operation may be discontinued.

Furthermore, when operating in the heating mode a modeled pressure at alocation downstream of the exterior heat exchanger may be used tocontrol operation of the heat pump circuit 204 (e.g., the compressor).For example, a temperature at the location indicated at 276 may bemodeled. The modeled temperature may then be used to control componentsin the compressor 228, for example, to alter the amount of heattransferred from the heat pump to the cabin heating circuit through thefirst refrigerant to coolant heat exchanger 226 (e.g., water cooledcondenser). Modeling the temperature at the location between the firstrefrigerant to coolant heat exchanger 226 (e.g., water cooled condenser)and the electrically operated heater 214 enables a temperature sensor,formerly at or near location 276, to be omitted from the system, ifdesired. As a result, the cost of the system may be decreased.Furthermore, modeling the temperature at the location 276 may allow formore accurate control of the heat pump system, thereby increasingcustomer satisfaction. Modeling the temperature in the cabin heatingcircuit, is described in greater detail herein with regard to FIG. 4.

FIG. 3 shows a cooling mode of operation for the climate control system200. In the cooling mode temperature reduced refrigerant (e.g., subcool)is transferred to the evaporator 232 from the first expansion valve 234(e.g., cooling expansion valve), indicated via arrow 300. It will beunderstood that the valve 289 may be closed or partially closed duringthe cooling mode of operation to prevent refrigerant bypass flow throughthe conduit 291. The evaporator 232 may be used to cool air provided tothe vehicle cabin 212, indicated via arrow 301. In this way, the heatpump's evaporator functions as a cooling core provided conditioned airto the cabin. Refrigerant is provided to the first expansion valve 234from the exterior heat exchanger 236, indicated via arrow 302.Additionally, refrigerant is provided to the exterior heat exchanger 236from the expansion valve 238, indicated via arrow 304. In the coolingmode heat is expelled from the exterior heat exchanger 236 to thesurrounding environment. Thus, in the cooling mode the exterior heatexchanger functions as a condenser. Additionally, in the system'scooling mode refrigerant is provided to the first refrigerant to coolantheat exchanger 226 from the compressor 228, indicated via arrow 306. Inthe depicted example, the cabin heating circuit 202 remains inactiveduring cabin cooling. Therefore, the first refrigerant to coolant heatexchanger 226 does not transfer a substantial amount of heat to thecabin heating circuit 202. Additionally, in the cooling mode refrigerantis flowed from the evaporator 232 to the accumulator 230 for thecompressor 228, as indicated via arrow 308.

To control the heat pump during the cooling mode a pressure may bemodeled at location 276, downstream of the exterior heat exchanger 236.Furthermore, the modeled pressure may be used to control operation ofthe first expansion valve 234 (e.g., cooling expansion valve) to adjustthe amount of refrigerant traveling through the evaporator 232. In thisway, cabin cooling may be accurately controlled to provide a desiredamount of cooling to the vehicle cabin. Various techniques for modelingthe pressure in the cooling mode are discussed in greater detail hereinwith regard to FIGS. 4-6. Additionally, it will also be understood, insome example, the cooling mode the heat pump circuit may besubstantially shut-down (e.g., not delivering heated coolant to thecabin heat exchanger).

FIGS. 1-3 show example configurations with relative positioning of thevarious components. If shown directly contacting each other, or directlycoupled, then such elements may be referred to as directly contacting ordirectly coupled, respectively, at least in one example. Similarly,elements shown contiguous or adjacent to one another may be contiguousor adjacent to each other, respectively, at least in one example. As anexample, components laying in face-sharing contact with each other maybe referred to as in face-sharing contact. As another example, elementspositioned apart from each other with only a space there-between and noother components may be referred to as such, in at least one example.Further still, an element shown within another element or shown outsideof another element may be referred as such, in one example. Furthermore,elements positioned upstream and downstream to one another with regardto fluid flow may be referred to as such. Additionally, component influid circuits, loops, etc., may have at least one inlet and at leastone outlet to allow the working fluid to flow through the components andtherefore these features of the components may be referred to as such.

FIG. 4 shows a method 400 for operating a climate control system. Itwill be appreciated that method 400 may be implemented via the climatecontrol system 200, illustrated in FIGS. 2 and 3 or, in other examples,may be implemented by other suitable climate control system.Instructions for carrying out method 400 and the rest of the methodsdescribed herein may be executed by a controller based on instructionsstored in memory (e.g., non-transitory) of the controller and inconjunction with signals received from sensors of climate controlsystem, such as the sensors described above with regard to FIGS. 2 and3. It will also be understood that the method steps may include thecontroller sending command signals to actuators in the commandedcomponent, the command triggering actuators in the commanded componentto adjust the component, as desired.

At 402 the method includes determining operating conditions in theclimate control system. The operating conditions may includetemperatures and pressures in the climate control system sampled fromsensors, for example. The operating conditions may further includeambient temperature, humidity, etc., that may be gathered via sensors.Additionally, the operating conditions may include vehicle cabin heatingand/or cooling requests (e.g., desired temperature set-point, desiredheating level, desired cooling level, etc.,) received by the controllerresponsive to user (e.g., driver, passenger, etc.,) interaction with aninput device (e.g., user interface, voice command interface, climatecontrol knobs, sliders, etc.) For instance, a user may interact with theinput device to request a desired cabin temperature (e.g., 70°, 75°,80°, etc.,) a level of cabin heating or cooling (e.g., a high cabinheating, low cabin heating, high cabin cooling, medium cabin cooling,90% heating, 10% cooling, etc.), etc.

Next at 404, the method determines if the climate control system isslated to be operated in a heating or cooling mode. Such a determinationmay be carried out, in one example, by determining if a cabin heating orcooling request, indicating a desire for cabin climate control, has beenreceived. In other examples, the cabin heating mode may be selected whenit is determined that the cabin temperature is less than a desiredvalue. On the other hand, in such an example, the cabin cooling mode maybe selected when it is determined that the cabin temperature is greaterthan the desired value.

If it is determined that the system slated to be operated in a heatingmode, the method advances to 406. More generally, the heating mode mayinclude steps 406-424. Furthermore, the heating mode and correspondingsteps may be implemented while a heating request is being receivedand/or the vehicle cabin temperature is below a target value.

At 406 the method includes operating an electrically operated heater(e.g., PTC heater) to heat a vehicle cabin. For instance, anelectrically operated heater may receive electric energy from the energystorage device and heat coolant delivered to a cabin heat exchanger(e.g., heater core). To elaborate, the output of the electricallyoperated heater may be adjusted using data from a temperature sensorcoupled to a coolant conduit downstream of the electrically operatedheater and upstream of the cabin heat exchanger for feedback heatercontrol. For instance, a temperature set-point, range, etc., may beestablished, if the measured temperature drops below the set-point theoutput of the electrically operated heater may be increased. Conversely,if the measured temperature is above the set-point the output of theelectrically operated heater may be decreased.

Next at 408 the method includes sampling or otherwise gathering datafrom a temperature sensor downstream of the electrically operated heaterand upstream of the cabin heat exchanger (e.g., at the outlet of theelectrically operated heater).

Next at 410 the method includes modeling a temperature downstream of thefirst refrigerant to coolant heat exchanger (e.g., water cooledcondenser) and upstream of the electrically operated heater in the cabinheating circuit.

Modeling the temperature may include steps 412 and 414. At 412 themethod includes determining a calibrated temperature table. Thecalibrated table may be calculated using the temperature from the sensordownstream of the electrically operated heater, the output (e.g., power,duty cycle, etc.,) of the electrically operated heater, and the speed(e.g., duty cycle) of the coolant pump in the cabin heating loop. Thecalibratable table may be a function of refrigerant to coolant heatingefficiency (based on compressor speed and pressure) and the temperatureof coolant entering the refrigerant to coolant heat exchanger 226. Thetemperature of the coolant entering the refrigerant to coolant heatexchanger 226 may be a function of coolant into the heater core andblower speed of cabin.

Next at 414, the method includes comparing a measured temperatureagainst the calibrated temperature table to determine the modeledtemperature at the location downstream of the first refrigerant tocoolant heat exchanger and upstream of the electrically operated heater.For instance, the modeled temperature may be determined by subtracting avalue from the calibrated table from the temperature sampled from thetemperature sensor downstream of the electrically operated heater. Inthis way, the modeled temperature may be efficiently ascertained.

At 416 the method includes operating the heat pump circuit based on themodeled temperature. Operating the heat pump circuit may include step418. At step 418, the method includes initiating heat pump feedbackcontrol using the modeled temperature. For example, the output of thecompressor in the heat pump circuit may be increased or decreased whenthe modeled temperature falls below or surpasses, respectively, aset-point value. In one specific example, the compressor may be operatedusing proportional-integral-derivative (PID) control. For instance,during PID control, the controller may calculate an error valverepresenting the difference between a desired set-point temperature andthe modeled temperature. Subsequently, the correction may be applied toproportional, integral, and derivative terms. However, numerous suitablecontrol schemes (e.g., feedback control schemes) of the compressor andother components in the heat pump system may be employed.

It will also be understood, that both heat pump circuit feedback controlusing the modeled temperature and feedback control of the electricallyoperated heater using the temperature sensor may be carried out inconjunction to achieve a desired heater core temperature. For instance,if the output of the compressor has reached an upper limit and theheater core has not achieved a desired temperature the output of theelectrically operated heater may be increased to enable the desiredheater core temperature to be quickly achieved. In one example, PTCheater control may be based on target vs actual heater core temperature.In such an example, the target heater core temperature may be sent fromthe climate control head based on driver input. Consequently, customersatisfaction can be increased.

At 420 the method includes determining if the cabin heat exchanger(e.g., heater core) is at a desired temperature set-point. If it isdetermined that the cabin heat exchanger is not at the desiredtemperature set-point (NO at 420), the method moves to 422. At 422 themethod includes maintaining current operating mode. For example, thecurrent operating mode may be a first sub-mode of cabin heating wherethe heat pump circuit is operated using feedback control with themodeled temperature and the electrically operated heater is controlledvia the feedback control strategy using the temperature sensor input.Thus, in the first sub-mode cabin heating occurs using the heat pump andthe electrically operated heater in tandem. It will be understood thatsteps 406-418 may be included in a first sub-mode of the system'sheating mode. After 422 the method may return to 420. However, in otherexamples, the method may return to 406 subsequent to 422 or may endafter 422.

On the other hand, if it is determined that the cabin heat exchanger hasreached the temperature set-point (YES at 420) the method advances to424. At 424, the method includes decreasing cabin heating viaelectrically operated heater. For instance, cabin heating via theelectrically operated heater may be phased out, discontinued, etc.

At 426, the method includes maintaining feedback control of heat pumpcircuit using the modeled temperature. In this way, heat pump circuitfeedback control may be maintained to keep the cabin temperature at thedesired level, within a desired range, etc., when the output of theelectrically operated heater is decreased or discontinued. The cabinmay, consequently, be quickly heated using the heat pump and theelectric heater and then the electric heater may be phased out, allowingfor a more efficient heat pump cycle to be used for cabin heating.Consequently, the system conserves energy enabling the vehicle's rangeto be extended in the case of a plug-in vehicle (e.g., BEV).

It will be understood that steps 424-426 may be included in a secondsub-mode of cabin heating operation. Furthermore, it will be appreciatedthat the system may transition between the first sub-mode of cabinheating and the second sub-mode of cabin heating or vice versa using acomparison between a cabin heating set-point and an actual vehicle cabintemperature. Additionally or alternatively, the first and secondsub-modes may be transitioned between based on state of charge of theenergy storage device. For instance, the second sub-mode may be selectedwhen the energy storage device state of charge falls below a thresholdvalue (e.g., 20 Amp-Hours, 50 Amp-Hours, 100 Amp-Hours, etc.).

If a cooling mode is selected at 404 the method proceeds to 428. It willbe understood that in method 400 the heating mode occurs while thecooling mode does not and vice versa. Furthermore, the modes may betransitioned between depending on changes in operating conditions (e.g.,when different sets of entry conditions are satisfied). For instance,the heating mode may be entered into when a cabin heating request isreceived and the cooling mode may be entered into when a cabin coolingrequest is received. However, in other examples the modal transition mayoccur automatically responsive to changes in coolant and/or refrigeranttemperatures in the system, ambient temperatures, etc. Therefore, thecontroller may differentiate between the heating and cooling modes insome instances. The different actions in the modes may be implementedwhile the entry conditions are occurring as well as other conditionstriggering specific actions in the modes. It will also be understoodthat the sub-modes, discussed herein, may also be transitioned betweenin a similar manner, in some instances.

At 428, the method includes sampling or otherwise collecting data from apressure sensor at an inlet and/or outlet of the first refrigerant tocoolant heat exchanger (e.g., water cooled condenser).

Next at 430, the method includes modeling a pressure downstream of theexterior heat exchanger and upstream of the first expansion valve (e.g.,cooling expansion valve). Modeling the pressure may include steps432-434. At 432, the method includes determining a calibrated pressuredrop table. The calibrated pressure drop indicates the pressure dropacross the exterior heat exchanger and therefore allows the pressure atthe outlet of the exterior heat exchanger to be determined when thepressure and/or temperature of refrigerant upstream of the exterior heatexchanger is known. The calibrate pressure drop table may be determinedusing, for example, compressor speed, the pressure of the refrigerantupstream of exterior heat exchanger (e.g., at a location between thesecond expansion valve and the first refrigerant to coolant heatexchanger), and/or ambient temperature. Specifically, in one example,the pressure drop may be generated using a table based on pressureupstream of the heat exchanger, ambient temperature, and airflow acrossthe heat exchanger. It will be understood that the airflow across theheat exchanger may be a function of vehicle speed and fan speed.

At 434, the method includes determining the modeled pressure using thepressure drop table and the sampled pressure (e.g., a pressure from thepressure sensor upstream of the exterior heat exchanger between thesecond expansion valve and the first refrigerant to coolant heatexchanger).

Next at 436 the method includes determining a subcool value from themodeled pressure and a temperature from a sensor downstream of theexterior heat exchanger, such as at the outlet of the exterior heatexchanger. To elaborate, the subcool may specifically be calculated byfirst converting the pressure at the outlet of the exterior heatexchanger to a condensing temperature and then subtracting thetemperature at the outlet of the exterior heat exchanger from thecondensing temperature, in one example. However, in other examples step436 may be omitted from the method.

At 438 the method includes operating the heat pump circuit based on themodeled pressure. Operating the heat pump may include step 440. At 440,the method includes initiating a heat pump feedback control strategyusing the modeled pressure. Specifically, in one example, the heat pumpcircuit may be operated based on the subcool value. For example, if thesubcool value is above a targeted set-point, ascertained from a cabincooling request, the first expansion valve (e.g., cooling expansionvalve) may be closed to a greater extent. On the other hand, if thesubcool value is below the targeted set-point, the first expansion valvemay be opened to a greater extent. In this way, the degree ofopening/closing of the first expansion valve may be adjusted to allowthe evaporator to provide a desired amount of cooling to the vehiclecabin, for example. It will be understood, that in other examples, thecompressor speed and/or degree of opening of the heating expansion valvemay also be operated based on the subcool value.

FIGS. 5 and 6 show graphical embodiments 500 and 600 of the heating andcooling modes, respectively, of the climate control system. In eachgraph time is indicated on the abscissa.

In FIG. 5, plot 502 indicates the operational state (i.e., an “ON” and“OFF” state) of the heating mode. As shown, the heating mode is on fromt0 to t2. Virtual temperature and compressor output are also indicatedon ordinates in graphs depicted in FIG. 5. Plot 504 indicates thevirtual temperature modeled using the previously described technique. Avirtual temperature set-point is indicated at 506. As shown, thecompressor output is varied to bring the virtual temperature in-linewith the virtual temperature set-point. In this way, compressor feedbackcontrol using the virtual temperature can be implemented.

In FIG. 6 plot 602 indicates the operational state (i.e., an “ON” and“OFF” state) of the cooling mode. As shown, the cooling mode is on fromt0 to t2. Subcool value and cooling expansion valve position andcompressor output are also indicated on ordinates in graphs in FIG. 6.Plot 604 indicates a subcool value and a subcool set-point is indicatedat 606. Plot 608 indicates expansion valve position. As previouslydiscussed, the subcool may be calculated using a temperature andpressure at the outlet of the exterior heat exchanger. As shown, theposition of the expansion valve is adjusted to move the subcool valuetowards the set-point 606.

The technical effect of modeling a temperature and/or a pressure in aclimate control system and then using the modeled values to control thesystem is to decrease system costs by reducing the number of sensorsused therein, if desired, as well as a potential increase in theaccuracy of cabin heating and cooling control in the system. Anothertechnical effect of modeling the pressure and/or temperature in theclimate control system may be to lower energy usage of the system whichmay result in increasing vehicle range when the vehicle is a plug-invehicle (e.g., BEV).

The invention is further described in the following paragraphs. In oneexample, a method for operating a vehicle climate control system isprovided that comprises: modeling a temperature in a cabin heatingcircuit coupled to a heat pump circuit via a refrigerant to coolant heatexchanger configured to transfer thermal energy between the heat pumpcircuit and the cabin heating circuit; and operating the heat pumpcircuit to deliver thermal energy to a cabin heat exchanger based on themodeled temperature. In one example, the method may further comprise,prior to operating the heat pump circuit, operating an electricallyoperated heater positioned downstream of the refrigerant to coolant heatexchanger to deliver thermal energy to the cabin heat exchanger. Inanother example, the method may further comprise decreasing an output ofthe electrically operated heater responsive to the vehicle cabinachieving a target temperature while the heat pump circuit continues tooperate to deliver thermal energy to the cabin heat exchanger tomaintain the target temperature.

In another aspect, a vehicle system is provided that comprises: anenergy storage device configured to deliver energy to an electric motorconfigured to deliver motive power to a drive wheel; a cabin heatingcircuit including: a cabin heat exchanger positioned downstream of arefrigerant to coolant heat exchanger in a heat pump circuit, therefrigerant to coolant heat exchanger transferring heat between a heatpump circuit in the heat pump circuit and the cabin heating circuit,where the heat pump circuit is configured to receive energy from theenergy storage device; and an electrically operated heater positionedbetween the refrigerant to coolant heat exchanger and the cabin heatexchanger; and a controller including instructions stored in memory thatwhen executed cause the controller to: model a temperature at a locationbetween the refrigerant to coolant heat exchanger and the electricallyoperated heater; and operate the heat pump circuit to deliver thermalenergy to the cabin heat exchanger using the modeled temperature.

In another aspect, a method for operating a climate control system in avehicle is provided that comprises: modeling a temperature at a locationbetween a refrigerant to coolant heat exchanger and an electricallyoperated heater fluidly connected to a cabin heat exchanger; operatingthe climate control system in a first mode responsive to a temperatureof a vehicle cabin being below a threshold value, in the first mode acompressor in a heat pump circuit is operated based on the modeledtemperature and the electrically operated heater is operated based on atemperature sensor downstream of the electrically operated heater andupstream of the cabin heat exchanger to increase the temperature of thevehicle cabin; and operating the climate control system in a second moderesponsive to the temperature of the vehicle cabin being at thethreshold value, in the second mode operation of the electricallyoperated heater is discontinued. In one example, the method may furthercomprise transitioning from the first mode to the second mode when thetemperature of the vehicle cabin reaches the threshold value wheretransitioning from the first mode into the second mode includesdecreasing an output of the electrically operated heater.

In another aspect, a method for operating a vehicle climate controlsystem is provided that comprises: modeling a pressure in a heat pumpcircuit downstream of an exterior heat exchanger and upstream of acooling expansion valve based on a pressure from a pressure sensorpositioned between a heating expansion valve and downstream of a watercooled condenser in the vehicle heat pump system; and in a cooling mode,adjusting an output of a cooling expansion valve in the heat pumpcircuit to cool a vehicle cabin based on the modeled pressure and atemperature from a sensor positioned upstream of the cooling expansionvalve and downstream of the exterior heat exchanger. In one example, themethod may further comprise transitioning into the cooling mode from aheating mode of the vehicle climate control system responsive toreceiving a cabin climate control adjustment request. In anotherexample, the method may further comprise operating a compressor in theheat pump circuit based on the modeled pressure. In yet another example,the method may further comprise operating a heating expansion valve inthe heat pump circuit based on the modeled pressure.

In another aspect, a vehicle system is provided that comprises: anenergy storage device configured to transfer energy to an electric motorconfigured to transfer motive power to a drive wheel; a cabin heatingcircuit including: a cabin heat exchanger positioned downstream of arefrigerant to coolant heat exchanger in a heat pump circuit, therefrigerant to coolant heat exchanger transferring heat between a heatpump circuit in the heat pump circuit and the cabin heating circuit,where the heat pump circuit is configured to receive energy from theenergy storage device; and an electrically operated heater positionedbetween the refrigerant to coolant heat exchanger and the cabin heatexchanger; and a controller including instructions stored in memory thatwhen executed cause the controller to: model a pressure in a heat pumpcircuit downstream of an exterior heat exchanger and upstream of acooling expansion valve; and in a cooling mode, operate the coolingexpansion valve in the heat pump circuit to cool a vehicle cabin and/ora vehicle battery based on the modeled pressure and a temperature from atemperature sensor positioned upstream of the cooling expansion valveand downstream of the exterior heat exchanger.

In another aspect, a method for operating a vehicle climate controlsystem is provided that comprises: modeling a pressure in a heat pumpcircuit downstream of an exterior heat exchanger an upstream of anexpansion valve; and operating the expansion valve in the heat pumpcircuit to cool a vehicle cabin based on the modeled pressure and atemperature from a sensor positioned upstream of the expansion valve anddownstream of the exterior heat exchanger. In one example, the methodmay further comprise operating a compressor in the heat pump circuitbased on the modeled pressure.

In any of the aspects or combinations of the aspects, the temperaturemay be modeled at an outlet of the refrigerant to coolant heatexchanger.

In any of the aspects or combinations of the aspects, the electricallyoperated heater may be operated based on temperature data from atemperature sensor coupled to a conduit extending between theelectrically operated heater and the cabin heat exchanger.

In any of the aspects or combinations of the aspects, modeling thetemperature may include determining a difference between a temperaturefrom a temperature sensor at an inlet of the cabin heat exchanger and acalibrated value.

In any of the aspects or combinations of the aspects, the calibratedvalue may be determined based on the temperature from the temperaturesensor, control commands of an electrically operated heater positionedbetween the refrigerant to coolant heat exchanger and the cabin heatexchanger in the cabin heating circuit, and control commands of a pumpin the cabin heating circuit.

In any of the aspects or combinations of the aspects, operating the heatpump circuit may include adjusting operation of a compressor in the heatpump circuit using a feedback control strategy.

In any of the aspects or combinations of the aspects, adjustingoperation of the compressor may include implementingproportional-integral-derivative (PID) control of the compressor usingthe modeled temperature.

In any of the aspects or combinations of the aspects, operating the heatpump circuit may include directing refrigerant from a compressor to therefrigerant to coolant heat exchanger and from the refrigerant tocoolant heat exchanger to an expansion valve and where the compressorincreases a pressure of the refrigerant flowing there through and theexpansion valve decreases the pressure of the refrigerant flowing therethrough.

In any of the aspects or combinations of the aspects, the controller mayfurther comprise instructions stored in the memory that when executedcause the controller to: operate the electrically operated heater todeliver thermal energy to the cabin heat exchanger in conjunction withthe operation of the heat pump circuit to achieve a cabin temperatureset-point.

In any of the aspects or combinations of the aspects, the controller mayfurther comprise instructions stored in the memory that when executedcause the controller to: decrease an output of the electrically operatedheater while maintaining operation of the heat pump to sustain the cabintemperature set-point in a vehicle cabin in response to achieving thecabin temperature set-point.

In any of the aspects or combinations of the aspects, modeling thetemperature may include determining a difference between a temperaturefrom a temperature sensor at an inlet of the cabin heat exchanger and acalibrated value and where the calibrated value is determined based onthe temperature from the temperature sensor, control commands of anelectrically operated heater positioned between the refrigerant tocoolant heat exchanger and the cabin heat exchanger in the cabin heatingcircuit, and control commands of a pump in the cabin heating circuit.

In any of the aspects or combinations of the aspects, the refrigerant tocoolant heat exchanger may be a water cooled condenser.

In any of the aspects or combinations of the aspects, the vehicle may bea hybrid vehicle including an internal combustion engine.

In any of the aspects or combinations of the aspects, modeling thetemperature may include determining a difference between a temperaturefrom a temperature sensor at an inlet of the cabin heat exchanger and acalibrated value.

In any of the aspects or combinations of the aspects, the calibratedvalue may be determined based on the temperature from the temperaturesensor, control commands of an electrically operated heater positionedbetween the refrigerant to coolant heat exchanger and the cabin heatexchanger in the cabin heating circuit, and control commands of a pumpin the cabin heating circuit.

In any of the aspects or combinations of the aspects, modeling thepressure in the heat pump circuit may include determining a pressuredrop across the exterior heat exchanger using a pressure from a pressuresensor positioned upstream of the exterior heat exchanger, a speed of acompressor in the heat pump circuit, and/or an ambient temperature.

In any of the aspects or combinations of the aspects, the refrigerant tocoolant heat exchanger may be a water cooled condenser coupled to acabin heating circuit and the cabin heating circuit is shut-down duringoperation of the expansion valve.

In any of the aspects or combinations of the aspects, operating theexpansion valve in the heat pump circuit may occur in a cooling mode ofthe vehicle climate control system and where the method furthercomprises transitioning the vehicle climate control system into thecooling mode from a heating mode responsive to receiving a cabin climatecontrol adjustment request.

In any of the aspects or combinations of the aspects, operating theexpansion valve may include increasing or decreasing a degree of openingof the expansion valve to increase or decrease an amount of refrigerantdelivered to an evaporator.

In any of the aspects or combinations of the aspects, the expansionvalve may be a cooling expansion valve and where operating the coolingexpansion valve in the heat pump circuit to cool the vehicle cabinincludes operating the cooling expansion valve using a subcool valuedetermined using the modeled pressure and a temperature from atemperature sensor downstream of the exterior heat exchanger.

In any of the aspects or combinations of the aspects, modeling thepressure in the heat pump circuit may include determining a pressuredrop across the exterior heat exchanger using a pressure from a pressuresensor positioned directly downstream or upstream of a refrigerant tocoolant heat exchanger and where the cabin heating circuit coupled tothe refrigerant to coolant heat exchanger is shut-down during operationof the cooling expansion valve.

In any of the aspects or combinations of the aspects, the controller mayfurther comprise instructions stored in the memory that when executedcause the controller to: transition between a heating mode of thevehicle system to the cooling mode responsive to receiving a cabinclimate control adjustment request.

In any of the aspects or combinations of the aspects, the refrigerant tocoolant heat exchanger is a water cooled condenser.

In any of the aspects or combinations of the aspects, the vehicle may bea hybrid vehicle including an internal combustion engine.

In any of the aspects or combinations of the aspects, the vehicle may bea battery electric vehicle.

In any of the aspects or combinations of the aspects, the water cooledcondenser may be coupled to the heat pump circuit and a cabin heatingcircuit and where the cabin heating circuit is shut-down while thepressure in the heat pump circuit is modeled.

In any of the aspects or combinations of the aspects, in the coolingmode refrigerant may be transferred from the cooling expansion valvedirectly to an evaporator.

In any of the aspects or combinations of the aspects, operating thecooling expansion valve in the heat pump circuit to cool the vehiclecabin may include operating the cooling expansion valve using a subcoolvalue determined using the modeled pressure and a temperature from atemperature sensor downstream of the exterior heat exchanger.

In another representation, a method for vehicle climate system controlis provided that includes calculating an outlet temperature of a watercooled condenser providing heat transfer functionality between a cabinheating loop and a heat pump loop without the use of a temperaturesensor at the outlet and using the calculated outlet temperature toadjust a compressor in the heat pump loop to achieve a desired vehiclecabin temperature.

In yet another representation, a method for vehicle climate systemcontrol is provided that includes calculating a pressure at an outlet ofan exterior heat exchanger functioning as a condenser in a heat pumploop without the use of a pressure sensor at the outlet of the exteriorheat exchanger and controlling operation of a cooling expansion valvepositioned downstream of the exterior heat exchanger using thecalculated pressure.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations, and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations, and/or functions may graphicallyrepresent code to be programmed into non-transitory memory of thecomputer readable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

As used herein, the term “substantially” is construed to mean plus orminus five percent of the range unless otherwise specified.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A method for operating a vehicle climatecontrol system, comprising: modeling a temperature in a cabin heatingcircuit coupled to a heat pump circuit via a refrigerant to coolant heatexchanger configured to transfer thermal energy between the heat pumpcircuit and the cabin heating circuit; and operating the heat pumpcircuit to deliver thermal energy to a cabin heat exchanger based on themodeled temperature.
 2. The method of claim 1, where the temperature ismodeled at an outlet of the refrigerant to coolant heat exchanger. 3.The method of claim 1, further comprising, prior to operating the heatpump circuit, operating an electrically operated heater positioneddownstream of the refrigerant to coolant heat exchanger to deliverthermal energy to the cabin heat exchanger.
 4. The method of claim 2,where an electrically operated heater is operated based on temperaturedata from a temperature sensor coupled to a conduit extending betweenthe electrically operated heater and the cabin heat exchanger.
 5. Themethod of claim 4, further comprising decreasing an output of theelectrically operated heater responsive to the vehicle cabin achieving atarget temperature while the heat pump circuit continues to operate todeliver thermal energy to the cabin heat exchanger to maintain thetarget temperature.
 6. The method of claim 1, where modeling thetemperature includes determining a difference between a temperature froma temperature sensor at an inlet of the cabin heat exchanger and acalibrated value.
 7. The method of claim 6, where the calibrated valueis determined based on the temperature from the temperature sensor,control commands of an electrically operated heater positioned betweenthe refrigerant to coolant heat exchanger and the cabin heat exchangerin the cabin heating circuit, and control commands of a pump in thecabin heating circuit.
 8. The method of claim 1, where operating theheat pump circuit includes adjusting operation of a compressor in theheat pump circuit using a feedback control strategy.
 9. The method ofclaim 8, where adjusting operation of the compressor includesimplementing proportional-integral-derivative (PID) control of thecompressor using the modeled temperature.
 10. The method of claim 1,where operating the heat pump circuit includes directing refrigerantfrom a compressor to the refrigerant to coolant heat exchanger and fromthe refrigerant to coolant heat exchanger to an expansion valve andwhere the compressor increases a pressure of the refrigerant flowingthere through and the expansion valve decreases the pressure of therefrigerant flowing there through.
 11. A vehicle system comprising: anenergy storage device configured to deliver energy to an electric motorconfigured to deliver motive power to a drive wheel; a cabin heatingcircuit including: a cabin heat exchanger positioned downstream of arefrigerant to coolant heat exchanger in a heat pump circuit, therefrigerant to coolant heat exchanger transferring heat between a heatpump circuit in the heat pump circuit and the cabin heating circuit,where the heat pump circuit is configured to receive energy from theenergy storage device; and an electrically operated heater positionedbetween the refrigerant to coolant heat exchanger and the cabin heatexchanger; and a controller including instructions stored in memory thatwhen executed cause the controller to: model a temperature at a locationbetween the refrigerant to coolant heat exchanger and the electricallyoperated heater; and operate the heat pump circuit to deliver thermalenergy to the cabin heat exchanger using the modeled temperature. 12.The vehicle system of claim 11, where the controller further comprisesinstructions stored in the memory that when executed cause thecontroller to: operate the electrically operated heater to deliverthermal energy to the cabin heat exchanger in conjunction with theoperation of the heat pump circuit to achieve a cabin temperatureset-point.
 13. The vehicle system of claim 12, where the controllerfurther comprises instructions stored in the memory that when executedcause the controller to: decrease an output of the electrically operatedheater while maintaining operation of the heat pump to sustain the cabintemperature set-point in a vehicle cabin in response to achieving thecabin temperature set-point.
 14. The vehicle system of claim 11, wheremodeling the temperature includes determining a difference between atemperature from a temperature sensor at an inlet of the cabin heatexchanger and a calibrated value and where the calibrated value isdetermined based on the temperature from the temperature sensor, controlcommands of an electrically operated heater positioned between therefrigerant to coolant heat exchanger and the cabin heat exchanger inthe cabin heating circuit, and control commands of a pump in the cabinheating circuit.
 15. The vehicle system of claim 11, where therefrigerant to coolant heat exchanger is a water cooled condenser. 16.The vehicle system of claim 11, where the vehicle is a hybrid vehicleincluding an internal combustion engine.
 17. A method for operating aclimate control system in a vehicle, comprising: modeling a temperatureat a location between a refrigerant to coolant heat exchanger and anelectrically operated heater fluidly connected to a cabin heatexchanger; operating the climate control system in a first moderesponsive to a temperature of a vehicle cabin being below a thresholdvalue, in the first mode a compressor in a heat pump circuit is operatedbased on the modeled temperature and the electrically operated heater isoperated based on a temperature sensor downstream of the electricallyoperated heater and upstream of the cabin heat exchanger to increase thetemperature of the vehicle cabin; and operating the climate controlsystem in a second mode responsive to the temperature of the vehiclecabin being at the threshold value, in the second mode operation of theelectrically operated heater is discontinued.
 18. The method of claim17, further comprising transitioning from the first mode to the secondmode when the temperature of the vehicle cabin reaches the thresholdvalue where transitioning from the first mode into the second modeincludes decreasing an output of the electrically operated heater. 19.The method of claim 17, where modeling the temperature includesdetermining a difference between a temperature from a temperature sensorat an inlet of the cabin heat exchanger and a calibrated value.
 20. Themethod of claim 19, where the calibrated value is determined based onthe temperature from the temperature sensor, control commands of anelectrically operated heater positioned between the refrigerant tocoolant heat exchanger and the cabin heat exchanger in the cabin heatingcircuit, and control commands of a pump in the cabin heating circuit.